Polyurethanes RIM processing

Unlike polyurethane-RIM processes, nylon-RIM reactions are endothermic and require temperatures of 130-140°C. In contrast to the polyurethane-RIM systems, this enables thick wall parts to be made. Cycle times of 2-3 minutes are comparable to those for polyurethane-RIM. In the development stage, current work is concerned with reducing moulding times and optimising moulding conditions. 

Figure 12.1 Example of typical polyurethane RIM processes (courtesy of Bayer)...

Finally, an update on more-recent commercial and experimental Dow Corning internal release agents, including two stream additives will be given. This paper should enable RIM processors to see how useful internal mold release agents can be in their polyurethane RIM process and the benefits they can realize by incorporating internal release agents into their systems. 

Macosko (1989) examined process modelling for RIM processes. Interestingly, the kinetic models examined here are pseudo-mechanistic, like the following for polyurethane RIM processing ... 

The RIM process was originally developed for the car industry for the production of bumpers, front ends, rear ends, fascia panels and instrument housings. At least one mass-produced American car has RIM body panels. For many of these products, however, a number of injection moulding products are competitive, including such diverse materials as polycarbonate/PBT blends and polypropylene/EPDM blends. In the shoe industry the RIM process has been used to make soling materials from semi-flexible polyurethane foams. 

The basic RIM process is illustrated in Fig. 4.47. A range of plastics lend themselves to the type of fast polymerisation reaction which is required in this process - polyesters, epoxies, nylons and vinyl monomers. However, by far the most commonly used material is polyurethane. The components A and B are an isocyanate and a polyol and these are kept circulating in their separate systems until an injection shot is required. At this point the two reactants are brought together in the mixing head and injected into the mould. 

The most successful application of the RIM-process is in the production of polyurethane-based materials. Other systems, such as composites based on polycaproamide, epoxy resins, and unsaturated polyesters can also be processed by reactive injection molding. New reactive systems have also been specially created for the RIM-process260 because of the exceptional opportunities it offers for manufacture of finished articles from engineering plastics with a high modulus of elasticity and impact strength. The automotive industry, which is the main customer for RIM-articles, can utilize this technology to manufacture of massive parts such as body panels, covers, wings, bumpers and other made of newly developed plastics. 

RIM Abbreviation for reaction injection molding. The RIM process involves the rapid metering and mixing of polyurethane reaction ingredients, followed by their injection into a mold. It allows the rapid production of molded polyurethane components. 

Thermoset polyurethanes are cross-linked polymers, which are produced by casting or reaction injection molding (RIM). For cast elastomers, TDI in combination with 3,3,-dichloro-4,4,-diphen5lmethanediamine (MOCA) are often used. In the RIM technology, aromatic diamine chain extenders, such as diethyltoluenediamine (DETDA), are used to produce poly(urethane ureas) (47), and replacement of the polyether polyols with amine-terminated polyols produces polyureas (48). The aromatic diamines are soluble in the polyol and provide fast reaction rates. In 1985, internal mold release agents based on zinc stearate compatibilized with primary amines were introduced to the RIM process to minimize mold preparation and scrap from parts tom at demold. Some physical properties of RIM systems are listed in Table 7. 

The GMP s process eliminates the use of sheet metal for the skin of the refrigerator door. In this application, the thermoplastic film forms a durable, protective outer skin with a wide choice of color options that are applied directly to the film. In addition more innovations exist apart from the film and thermoplastic interior liner, the doors consist entirely of polyurethane. GMP backs the thermoplastic film with an approximately 4 mm thick layer of the Baydur 110 structural foam polyurethane RIM system from Bayer AG that creates a rigid, dimensionally stable outer shell with no need for sheet metal. Then, GMP fills the space between this shell and the inner liner with insulating polyurethane foam, a rigid, low-density foam. The result is a self-supporting door that satisfies all stability, thermal insulation, and surface finish requirements. 

This durable, new composite is extremely strong, and yet it weighs 25% less than steel. Some HarvestForm panels will utilize Bayer s Baydur structural foam polyurethane RIM system, which utilizes a soybean-based polyol component. This structural foam PUR RIM formulation is based on soybeans that would produce physical properties and processing parameters equivalent to Bayer s conventional formulations. 

Tables VII and VIII sumnarize present and future RIM engineering plastic developments. This is an emerging area for RIM processable materials part of which will be made possible by recent equipment developments such as hot RIM. Polyurethane materials which now exist in this hard segment range are plastics...

A further example of the new materials research being done on RIM processable polymers are the high modulus urethane -epoxy UN s, shown in Table IX (12). These materials are shown compared to a toughened plastic polyurethane 146,000 psi flexural modulus urethane naterial. The urethane-epoxy IEN s are based on two epoxies (Bisphnol A type and Novalak type). 

Although polyurethane has been the principle polymer commercialized 1n the RIM process, modified polyurethane and... 

The successful utilization of Reaction Injection Molding (RIM) to fabricate complex polyurethane shapes In a single step from relatively low viscosity streams has led to a search for other chemical systems which can be fabricated by the RIM process. The rapid polymerization of molten caprolactam by anionic catalysis has been utilized to develop attractive nylon RIM systems. The incorporation of a rubber segment In the polymer chain allows the fabrication of high Impact or even elastomeric nylon parts. The combination of a rubber phase with the high melting (215°C) crystalline nylon phase provides useful properties at low temperatures as well as at elevated temperatures. 

E-9031,9053,9092. [lO Polyurethanes] Imine-polyuiea system used for RIM processing for automotive exterior an>lics. 

RIMIine . [ICI Polyurethanes] Polyurethane or polyurea systems for RIM processing. 

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